Process of preparing resin from a diepoxide



United States Patent O 3,370,019 PROCESS OF PREPARING RESIN FROM A DIEPOXIDE Walter H. Schuller and Ray V. Lawrence, Lake City, Fla., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Original application Apr. 2, 1964, Ser. No. 356,987. Divided and this application Dec. 4, 1964, Ser.

1 Claim. (Cl. 260-2) ABSTRACT OF THE DISCLOSURE This invention relates to the formation of resinous products obtained by resinifying the mixed diepoxides resulting from the thermal rearrangement of the mixed transannular peroxides of photosensitized oxidized pine gum with borontrifluoride ehterate. These mixed diepoxides contain carboxylic acid groups. The resulting resinous products are hard, glossy, and useful in surface coatings.

A nonexclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicense for such purposes, is hereby granted to the Government of the United States of America.

This application is a division of Ser. No. 356,987, filed Apr. 2, 1964.

This invention relates to the new and useful diepoxide (I) and to its esters and salts. More pecifically, it relates to a process for preparing (I) by means of the thermal rearrangement of 6,14-peroxy-A' -dihydroabietic acid (H), by heating (II) in an inert solvent. The diepoxides (I) have a variety of commercial uses including the preparation of casting resins, laminating resins, adhesives, and may be combined with HA-type reagents to give surface coatings, as will be discussed more fully below.

The structure of the diepoxide, sometimes referred to below as the free acid, is (I) H30 0 OOH I ice It exhibits [a] I 10l (.l% in ethanol), M +305. The numbering system is according to 'W. Klyne, J. Chem. Soc., 3072 (1953).

As used herein, the term levopimaric acid transannular peroxide (II) is meant to include not only the transannular peroxide of levopimaric acid, but also the mixed transannular per-oxide of photosensitized oxidized pine gum. The above products will be discussed more fully below.

The preparation of levopimaric acid transannular peroxide (II) and the transannul-ar peroxides of photosensitized oxidized pine gum may be prepared according to US. Patent No. 2,996,515, issued Aug. 15, 1961. The process involves a photosensitized oxidation whereby pine gum in a solution containing a small amount of a sensitizing dye, such as rose bengal, is simultaneously aerated and irradiated with visible light.

The process of the thermal rearrangement of levopimaric acid transannular peroxide (II) can be carried out in any suitably inert solvent, such as toluene, ortho-, meta-, para-, or mixed xylenes, cumene, pseudocumene, alkylated benzenes of all types, anisole, phenetole, etc. One of the more satisfactory solvents is mixed xylenes having a boiling point at about 138 C.

The temperatures at which the thermal rearrangement can be carried out may be varied from about 110 C. to about 265 C. using an oil bath with a preferable range of about l30l60 C. At 138 C. the reaction requires about 10 hours to go to approximate completion. If higher temperatures are used, shorter heating times are required and, conversely, if lower temperatures are employed longer reaction periods are necessary for complete conversions. It is an advantage of our process that the rate and completeness of the reaction are easily controlled by determining the optical rotation [11113 of the solution.

The concentration of the levopimaric acid transannular peroxide in the inert solvent should generally not exceed 4% as side reactions or subsequent reactions then become undesirable in amount. A preferable concentration of the peroxide in mixed xylene for a reaction at about 138 C. is about 23%, 2.5%, causing excellent results to be obtained.

Upon completion of the thermal rearrangement of the diepoxide, as may be determined by its optical rotation, it may be converted to an amine salt, e.g., a tertiary butyl amine salt. This is done by the addition of about 20% excess of the stoichiometrical amount of a soluble lower alkyl amine having one to eight carbon atoms required to react with the diepoxide. The amine salt may then be separated from the solution.

The thermal rearrangement of the alkyl esters of levopimaric acid transannul-ar peroxide gives products differing from those obtained by the thermal rearrangement of the free acid. One product obtained by the process using the methyl ester as the starting material has the following properties after one crystallization from aqueous ethanol: M.P. l35-l43 C.; [a] -157 (c. 1.0 in ethanol); no characteristic absorption from 220-320 no peroxide content; A max (Nujol mull) 8.06, 11.12, 11.45, 11.68 essentially no absorption from 220-320 The product of photosensitized oxidized pine gum consists essentially of a mixture of transannular peroxides from levopimaric acid, palustric acid, and neoabietic acid [(cf. J. Am. Chem. Soc., 80, 1483 (1958); ibid., 82, 1734 (1960); ibid., 83, 2563 (1961)]. On heating this photosensitized oxidized pine gum in an inert solvent, such as mixed xylenes at about 138 C., all of the peroxide content is lost and a product consisting of a mixture of diepoxides, including the one from levopimaric acid transannular peroxide is obtained. This mixture of diepoxides is of considerable interest commercially due to its low cost of preparation, being prepared in only two steps from the low-cost, crude, pine gum raw material. The use of this mixture of the diepoxides as additives to asphalt in preparing nonskid surfaces for roads is a demonstrated outlet for a cheap source of such a mixture of diepoxides and is also an embodiment of our invention.

The following examples are set forth by way of illus tration only and it will be understood that the invention is not to be construed as limited in spirit or in scope by the details therein. Temperatures are given in degrees centigrade. The following abbreviations are employed: M.P. means melting point; neut. equiv. is neutral equivalent; n.m.r. (or N.M.R.) is nuclear magnetic resonance expressed as T (tau); 95% ethanol means 95% ethanol plus 5% water.

Melting point (M.P.) is determined by means of a Thomas Hoover Melting Point Apparatus; via standard equipment infrared max (Nujol mull) via Perkin-Elmer Model 21 infrared spectrophotometer; n.r.m. by means of a Varian A-60 spectrophotometer.

Example 1 A solution of 2.5 grns. of levopimaric acid transannular peroxide in 125 ml. of mixed xylenes is refluxed at about 138 C. The reaction is followed by a change in the optical rotation of the solution. A plot of optical rotation vs. time, levels off in about hours at [a] 49; refluxing is continued for 4 more hours with little change in value of [a] The peroxide content is essentially zero in 12 hours. A crystalline tertiary butylamine salt of the product is obtained in 95% yield by weight.

The salt is recrystallized to constant optical rotation from acetonitrile; yield 2.14 g. (71%); M.P. 183 186 C. decomposes with evolution of gas; [04],; 42.7 (c. 0.91 in 95% ethanol); no characteristic absorption from 220 320a; max (Nujol mull) 6.87 (m), 11.88 (w), 12.0 (w) ,u.. Analysis.Calcd. for C H ON: C, 70.7; H, 10.1; N, 3.44; O, 15.7; neut. equiv. 408. Found: C, 70.5; H, 10.1; N, 3.65;O, 15.8; neut. equiv. 408.

The free acid is liberated from the above salt in 98% yield using dilute phosphoric acid in water. 1.5 g. of the salt is agitated in a solution of 0.48 ml. cone. phosphoric acid (50% excess) in 50 ml. of water and 50 ml. either. An analytical sample was recrystallized to constant optical rotation from di-n-propyl ether and then from aqueous methanol; M.P. 172-174 C. decomposes with evolution of gas; [(11 70.3 (c. 0.80 in 95% ethanol); no characteristic absorption from 220-32Qa; m A max (Nujol mull) 6.92 (shoulder), 8.88 (w), 11.1 (w), 11.9 (w), 12.0 (w) a. Analysis.Calcd. for C H O C, 71.8; H, 9.0; O, 19.1; neut. equiv. 334.4. Found: C, 71.6; H, 9.2; O, 19.3; neut. equiv. 335.5.

Example 2 A portion of the free acid of Example 1 is used for the preparation of the methyl ester by reaction with diazomethane to give a pure product of unchanged M.P. on recrystallization from aqueous methanol; M.P. 121 C.; 72.4 (c. 0.60 in 95% ethanol); no absorption from 220-320 m max (Nujol mull) 7.0 (m), 8.04 (s), 8.82 (m), 11.07 (m), 11.85 (w), 11.97 (w) a no bands in 3 region; I1.II1.I.'r=6.99 (1 proton; hydrogen on carbon bearing an ox gen function), a doublet superimposed on a second doublet at about 1-=7.13, 7.23 (total area equivalent to 1 proton; a hydrogen on carbon bearing an oxygen function split by two nonequivalent adjacent hydrogens). Analysis.Calcd. for C l-I 0; C, 72.4; H, 9.3; O, 18.4. Found: C, 72.3; H, 9.5; O, 18.2.

Example 3 A solution of 5 g. of levopimaric acid transannular peroxide in 125 ml. of cumene is held at 138 C. and the reaction is followed by the change in optical rotation. After a low of [ab 43 at eleven hours, the rotation rises to 41 at twelve hours, whereupon the reaction is stopped and the tertiary-butylamine salt obtained in yield. After recrystallization from acetonitrile the salt is obtained in 60% overall yield (3.66 g.); --43 (0. 1.0 in ethanol).

Example 4 A solution of 3.5 g. of levopimaric acid transannular peroxide in ml. of pseudocumene is held at C. in an oil bath. The reaction is followed by means of the change in optical rotation. The rotation levels off at [0:1 50 in about 9 hours, whereupon heating is stopped. The tertiary-butylamine salt is prepared in 95% yield and recrystallized from acetonitrile to give 2.77 g. (65%) of pure salt.

Other organic amines including cyclohexylamine, 2- amino-2-methyl-l-propanol, etc., may be substituted for the tertiary-butylamine.

Example 5 A solution of 2.5 g. of levopimaric acid transannular peroxide in 125 ml. of mixed xylenes is refluxed at 138 C. for 12 hours. The rotation is -49 at this point, and the reaction is stopped. The tertiary-butylamine salt is prepared in 95% yield by adding 0.93 ml. (20% excess) of tertiary-butylamine and diluting the solution to one liter with pentane. On chilling, 2.89 g. (95 of the salt is obtained. After recrystallization from acetonitrile the salt weighs 1.83 g. (60%); [0:1 43 (0. 1.0 in 95% ethanol).

Example 6 A solution of 5 g. of photosensitized oxidized pine gum (prepared according to US. Patent 2,996,515) containing 0.50 equivalent of peroxide/ mole of resin acid in 125 ml. of mixed xylenes is rehuxed at 138 C. for 12.5 hours at which time all of the peroxide content has essentially disappeared as determined by titration by means of the method of Schuller and Lawrence, J. Am. Chem. Soc., 83, 2563 (1961). The solvent is removed by stripping under reduced pressure and the residual syrup is dried in vacuo to give a friable solid which is soluble in ethanol, methanol, benzene, and acetone, but insoluble in water and isooctane. Because of its low cost, it is especially useful for addition to asphalts to provide nonskid surfaces on sidewalks and highways.

Example 7 A portion of the product of Example 6 is treated by the addition of 5% of boron-trifiuoride etherate (a commercially available product), heating for 10 minutes at 100 C., and then for six hours at C. A hard, glossy resin is obtained useful in surface coatings.

We claim:

1. A resinous composition produced by:

(a) heating a solution containing about from 2 to 4% by weight in an inert organic solvent of the mixed transannular peroxides resulting from the photosensitized oxidation of pine gum, with stirring, to a temperature of about from 110 to 265 C. to thermally rearrange said mixed transannular peroxides to the corresponding mixed diepoxides;

(b) continuing the heating at said temperature until the peroxide content is reduced essentially to zero;

(c) removing the solvent under reduced pressure;

(d) recovering the mixed diepoxides by drying in vacuo;

(e) mixing said recovered diepoxides with about 5% by weight of borontrifluoride etherate;

(f) heating said diepoxide-etherate mixture for about 10 minutes at 100 C.; and then (g) raising the temperature to about 160 C. for about OTHER RSFERENCES 6 to resinify the mixture- Hawkins: Organic Peroxides, 1961, pp. 243-245, 248

References Cited relied UNITED STATES PATENTS 5 WILLIAM H. SHORT, Primary Examiner. 2,996,515 8/1961 Moore et a1. 26099 PERTILLA, Assistant Examiner 3,143,578 8/1964 OConnor et a1. "260-2 

